A TERMINAL MORAINE IN CENTRAL INDIANA.
It has been said in another part of this volume, that the Drift material.
which overlies so great an area in Indiana, has been modified by the
action of the post-glacial forces to such an extent that it is extremely dif:"
ficult to trace many of its original outlines; but there is a well-defined
and most interesting moraine, or. tangle of moraines, which lies in the
form of an obtuse angle, whose lines cut the eastern and western border
of the State and whose apex points southward. It passes iIlto Illinois
from Warren and Benton counties, and into Ohio from Randolph and
Wayne counties. It is most obscure at its apex and most clearly defined
along its western member in Tippecanoe, Clinton, Montgomery and Boone
counties, and along its eastern member in HeJ?ry; Wayne and Randolph
counties. The mass of this moraine is enormous, and at many points is
heavily charged with bowlders mostly of igneous and crystalline formation, though a considerab1e number of large limestone fragments, chiefly
Devonian and Upper Silurian, are found. Southward from the line of
this moraine the Drift mass gradually thins out and finally disappears,
and northward from it the depth of the Drift diminishes for a distance
and then increases again. The valley of the .Wabash is cut through the
moraine in Tippecanoe County. The cuttings of the L., N. A & C.
Railroad south of Lafayette show, in a very interesting way, the structure of the mass and the manner iIi which its surface has been modified
by the action of water and by the operation of freezing and thawing. In
the western part of Clinton County, and in the northern portion of Montgomery and Boone counties, the bowlder clay is immediately under the
, surface soil, and here great areas are thickly strewed with heavy granitic
and gneissic bowlders. In Benton County a heavy swell or ridge of
morainic material is the chief feature observable, while in Marion and
Hendricks counties· the Drift mass, though very thick in a general way,
is superficially a great rolling plain cut through by numerous streams, the
principal of which is White River. From Marion County through Hancock, Henry, Wayne anq Randolph counties the Drift mass, though variable, preserves its morainic character. The foregoing rough description
will be sufficient to eooble the reader to trace on any map of Indiana th~
general course of the moraine and to note its position with reference t.
-
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REPORT OF STATE GEOLOGIST.
the trend of the Wabash Valley. It must not be understood, however,
that the moraine, in regard to its width or cross-section, is confined to the
counties indicated; indeed, the deposit is of immense proportions, spreading over, besides the counties named already, a part of Newton, Warren,
Fountain and C~rroll counties, the southern. part of Howard, and parts
{)f Tipton, Hamilton, Madison, Jay and Delaware, with a projection at
its apex into Morgan, Johnson, ShelBy and Rush counties. At first
glance this will appear to give very little symmetry of outline, and, indeed', the form of the mass as it n,oW lies represents no more than the '
base of what was, at the close of the glacial period, a low, knobby or
hilly ridge spanning the State at the angle indicated. The modification
which this moraine has undergone since the return of a temperate climate
has been in the direction of spreading and flattening the mass and of
cutting many deep and oftentimes eccentric water channels in it. This
modification is still going on as the res~dt of the action of wind, rain and
freezing and thawing.
No doubt the far greater part of this leveling and spreading process
was accomplished during the long and necessarily dreary period between
the time when the glacier withdrew from Indiana and that when the Drift
.area was covered with vegetation. This barren period. must have been
one of much greater extent than geologists have been inclined to admit,
.and if we take the rainfail as averaging as grcat as we now have, we can
€asily see how a vast heap or ridge of bowlder till, moraine dust and
{)ther debris, with no vegetation to protect it, wo'uld be rapidly reduced to.
a comparatively level mass.
To my mind the evidence is clear that what I here describe as a terminal moraine is really an accumulation of moraines, the effect of many
glacial advances, retreats and returns during the great ice period. No
doubt, at times when the morainic mass was frozen to adamantine hardness and there came a vigorous return of the glacier, the ice flowed over
the huge barrier itself had formerly made and slowly ground it to .!llower
level. It is only by understanding this pendulum-like oscillation of the
glaciers through a vast period of time that we can solve the problem of
the intercalated lenticular magses of sand and water-bearing gravel found
hermetically sealed within the blue clay of the Drift, as is shown in a
foregoing chapter.
By referring to Dr. Phinney's report of his examinations in Henry and
Randolph counties, it will be seen that he found the moraine well marked
in its development. So in Dr. Brown's survey of Hancock, and in the
reports upon Clinton, Tippecanoe and Benton counties by Prof. Gorby
.and W. H. Thomp8on, the features of the formation are minutely described. The highest part of the moraine is in Randolph County perhaps,
where it forms the divide between the waters ultimately flowing into
White and White Water rivers.
MORAINE IN CENTRAL INDIANA.
59
The Wabash River has cut its way through the great moraine, chiefly
in Tippecanoe, Fountain and Warren counties. West of the river from
Lafayette the high, ·picturesque knobs, overlooking the beautiful city and
grand channel of the Wabash for miles, are heaps of Drift matter, showing every characteristic of moraine formation, while south of the city,
near the Junction, the recent terraces are heaped against. immense masses.
of' bowlders aJ;ld bowlder clay.
It is a curiously suggestive· fact in this connection that White River.
Sugar Creek and Wabash River (each in its turn) will be found, upon
glancing at any map of the State, running in the higher parts· of their
course, parallel with the general trend of the eastern limb of the moraine
and breaking through the formation to immediately take a more southerly
course. This would seem to indicate that the moraine had acted as an
obstruction to each of these streams for a time, and that they had all fol-·
lowed the northern side of it until some weak point was found through
which a passage was forced by each in its own way.
A careful study of the Wabash River shows that its passage through
the great rock dam and through the moraine are completed at the samepoint near Covington, in Fountain County, where the river turns into a.
eourse nearly due south; and it is this great rock dam at Momence, in
Illinois, which the Kankakee must be made to o.vercome before its vast
area of wet lands'can be drained successfully.
Students of geology, who desire to give especial study to the more,marked features of the great moraine herein so roughly and hastily
sketched, will find Lafayette Junction, the eastern part. of Clinton County.
the northern part of Montgomery County and a large part of Wayne and
Randolph ·counties the most favorable points of attack, and it is to behoped that the students and scientists of the State will give this very interesting geological feature a patient and careful investigation.
The· line of distllrbance triwed by Prof. Gorby across the State appearilto bear, a close relation to the formation of this terminal moraine. No.
doubt the great rock barrier formed a sort of dam against the free advance of the glacier, and thus it modified, in a large degree, the Drift or
morainic formation in the first place, and afterward controlled the floods
of iceberg-bearing water, Which rushed southward from the foot of the
retreating glacier, thus preventing the total destruction of the moraine's
outlines by this agency and giving direction to the Wabash and Whiterivers. Indeed, evidence is present everywhere along the formation going to show that the northern rim of the moraine became the stranding
. place of icebergs loaded with bowlders, and that this stranding line was
practically parallel with Fhe flow of the Wabash, and with the trend of
the great rock dam. Crowning the very highest parts of the moraine are
found so-called dykes of great extent, formed chiefly of granitic bowlders.
These bowlder areas, as I prefer to call them, are not areas of erosion.
REPORT OF STATE GEOLOGIST.
-0n the contrary they are often deposits, and passing over the highest
:swells of the formation. I had the pleasure and profit of going over one of
these areas with Prof. Chamberlain, of the United States Geological Survey. This was in the northern part of Montgomery County, wltere the
so-called" Bowlder Dyke" practically ends.
I have, for mere convenience, called the morainic mass, thus roughly
~utlined, a terminal moraine; but I regard it as a cluster or tangle of a
number of inseparable moraines, caused chiefly by the separating of the
.great glacier into lobes, and by successive advances and retreats of the
ice masses, attended by great rivers of rapidly rushing water in the melting periods. One of the marked features of thiR formation is a succession
~f knobs or cones of sand and gravel, alternating irregularly with ridges
and hills of bowlder clay, and with occasional undrained areas or basins.
Of course, to outline this great deposit with any close attention to deMils would require a minuteness of examination and an amount of time
.1Uld expense wholly out of the limits set by my duties. I hope that
this sketch will induce others to make a study of what is the most inter.esting scientific problem in connection with the superficial geology of In«iana.